Hi Parade,
When you say in OO Spreadsheet do you mean Calc
If so go to tools > Options > OpenOffice.org Calc > expand it and select
Sort Lists > New.
You can then input the days of the month and it will then allow you to sort either 1-31 or 31-1 etc. bear in mind you will need to adjust for the "short months"
Register for the openoffice forum at openoffice.org its free and is actually used by the developers at SUN MICROSYSTEMS (and their internal StarOffice Support Guru's as its the same source code)
Hope this helps
WallacetheGreat